In recent years color printers that emit colored inks from a print head are coming into widespread use as computer output devices. Among such printers, there are those that are equipped with the ability to print bidirectionally in order to improve printing speed.
A problem that readily arises in bidirectional printing is that of deviation in printing position in the main scanning direction between forward and reverse printing passes. Causes of this deviation include backlash in the main scanning drive mechanism, stretching of the carriage belt, and warping of the platen on which the printing medium rests. Japanese Patent Laid-open Hei 5-69625 is an example of a technology disclosed by the present applicants for solving this problem of printing deviation. This comprises of registering beforehand the printing deviation amount in the main scanning direction and using this printing deviation amount as a basis for correcting the printing position on the forward and reverse passes.
However, various printing media are used including A3 size paper, A4 size paper and postcards. For printing, A3 and A4 sheets are generally inserted into approximately the center of the main scanning stroke range of the printer, while postcards are inserted at one end. Printing deviation tends to be particularly large at each end of a printer's main scanning stroke. Thus, while printing deviation may be properly adjusted for an A4 or A3 sheet, it is difficult to properly adjust for printing deviation in the case of postcards.
An object of the present invention is to provide a new technology for reducing printing position deviation in the main scanning direction between forward and reverse passes in a printer that prints bidirectionally.